Work vehicle magnetorheological fluid joystick systems providing machine state feedback

ABSTRACT

Embodiments of a work vehicle magnetorheological fluid (MRF) joystick system include a joystick device, an MRF joystick resistance mechanism, a controller architecture, and a work vehicle sensor configured to provide sensor data indicative of an operational parameter pertaining to work vehicle. The MRF joystick resistance mechanism is controllable to vary an MRF resistance force resisting movement of a joystick included in the joystick device relative to a base housing thereof. The controller architecture is configured to: (i) monitor for variations in the operational parameter utilizing the sensor data; and (ii) provide tactile feedback through the joystick device indicative of the operational parameter by selectively commanding the MRF joystick resistance mechanism to adjust the MRF resistance force impeding joystick movement based, at least in part, on variations in the operational parameter.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. provisional application Ser.No. 63/019,083, filed with the United Stated Patent and Trademark Officeon May 1, 2020.

STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE DISCLOSURE

This disclosure relates to magnetorheological fluid (MRF) joysticksystems, which selectively vary joystick resistances to provide feedbackindicative of monitored operational parameters or machine states of workvehicles.

BACKGROUND OF THE DISCLOSURE

Joystick devices are commonly utilized to control various operationalaspects of work vehicles employed within the construction, agriculture,forestry, and mining industries. For example, in the case of a workvehicle equipped with a boom assembly, an operator may utilize one ormore joystick devices to control boom assembly movement and, therefore,movement of a tool or implement mounted to an outer terminal end of theboom assembly. Common examples of work vehicles having suchjoystick-controlled boom assemblies include excavators, feller bunchers,skidders, tractors (on which modular front end loader and backhoeattachments may be installed), tractor loaders, wheel loaders, andvarious compact loaders. Similarly, in the case of dozers, motorgraders, and other work vehicles equipped with earth-moving blades, anoperator may utilize with one or more joysticks to control blademovement and positioning. Joystick devices are also commonly utilized tosteer or otherwise control the directional movement of the work vehiclechassis in the case of motor graders, dozers, and certain loaders, suchas skid steer loaders. Given the prevalence of joystick devices withinwork vehicles, taken in combination with the relatively challenging,dynamic environments in which work vehicles often operate, a continueddemand exists for advancements in the design and function of workvehicle joystick systems, particularly to the extent that suchadvancements can improve the safety and efficiency of work vehicleoperation.

SUMMARY OF THE DISCLOSURE

A work vehicle magnetorheological fluid (MRF) joystick system isdisclosed for usage onboard a work vehicle. In embodiments, the workvehicle MRF joystick system includes a joystick device, an MRF joystickresistance mechanism, a controller architecture, and a work vehiclesensor configured to provide sensor data indicative of an operationalparameter pertaining to the work vehicle. The joystick device includes,in turn, a base housing, a joystick movably mounted to the base housing,and a joystick position sensor configured to monitor movement of thejoystick relative to the base housing. The MRF joystick resistancemechanism is controllable to vary an MRF resistance force inhibiting orresisting movement of the joystick relative to the base housing in atleast one degree of freedom (DOF). The controller architecture iscoupled to the joystick position sensor, to the work vehicle sensor, andto the MRF joystick resistance mechanism. The controller architecture isconfigured to: (i) monitor for variations in the operational parameterutilizing the sensor data; and (ii) provide tactile feedback through thejoystick device indicative of the operational parameter by selectivelycommanding the MRF joystick resistance mechanism to adjust the MRFresistance force based, at least in part, on variations in theoperational parameter.

In further embodiments, the work vehicle MRF joystick system includes ajoystick device, an MRF joystick resistance mechanism, and a controllerarchitecture. Once again, the joystick device includes a base housing, ajoystick movably mounted to the base housing, and a joystick positionsensor configured to monitor movement of the joystick relative to thebase housing. The MRF joystick resistance mechanism is controllable tovary an MRF resistance force resisting movement of the joystick relativeto the base housing in at least one DOF. The controller architecture,coupled to the joystick position sensor and to the MRF joystickresistance mechanism, is configured to: (i) monitor a current groundspeed of the work vehicle; and (ii) selectively command the MRF joystickresistance mechanism to adjust the MRF resistance force based, at leastin part, on the current ground speed of the work vehicle.

In still further embodiments, the MRF joystick system is utilizedonboard a work vehicle equipped with a boom-mounted implement. The MRFjoystick system includes a joystick device, an MRF joystick resistancemechanism, and a controller architecture. The joystick device includes,in turn, a base housing, a joystick movably mounted to the base housing,and a joystick position sensor configured to monitor movement of thejoystick relative to the base housing. The MRF joystick resistancemechanism is controllable to vary an MRF resistance force resistingmovement of the joystick relative to the base housing in at least oneDOF. Coupled to the joystick position sensor and to the MRF joystickresistance mechanism, the controller architecture is configured to: (i)estimate a variable load resisting movement of the boom-mountedimplement in at least one direction, and (ii) selectively command theMRF joystick resistance mechanism to increase the MRF resistance forceas the variable load increases.

The details of one or more embodiments are set-forth in the accompanyingdrawings and the description below. Other features and advantages willbecome apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

At least one example of the present disclosure will hereinafter bedescribed in conjunction with the following figures:

FIG. 1 is a schematic of an example magnetorheological fluid (MRF)joystick system onboard a work vehicle (here, an excavator) andconfigured to provide machine state feedback through variations injoystick stiffness, as illustrated in accordance with an exampleembodiment of the present disclosure;

FIG. 2 is a perspective view from within the excavator cabin shown inFIG. 1 illustrating two joystick devices, which may be included in theexample MRF joystick system and utilized by an operator to controlmovement of the excavator boom assembly;

FIGS. 3 and 4 are cross-sectional schematics of the example MRF joysticksystem, as partially shown and taken along perpendicular section planesthrough a joystick included in a joystick device, illustrating onepossible construction of the MRF joystick system;

FIG. 5 is a process suitably carried-out by the controller architectureof the MRF joystick system to vary joystick stiffness in a mannerproviding machine state feedback; and

FIG. 6 is a graphic illustrating, in a non-exhaustive manner, additionalexample work vehicles into which embodiments of the MRF joystick systemmay be beneficially integrated.

Like reference symbols in the various drawings indicate like elements.For simplicity and clarity of illustration, descriptions and details ofwell-known features and techniques may be omitted to avoid unnecessarilyobscuring the example and non-limiting embodiments of the inventiondescribed in the subsequent Detailed Description. It should further beunderstood that features or elements appearing in the accompanyingfigures are not necessarily drawn to scale unless otherwise stated.

DETAILED DESCRIPTION

Embodiments of the present disclosure are shown in the accompanyingfigures of the drawings described briefly above. Various modificationsto the example embodiments may be contemplated by one of skill in theart without departing from the scope of the present invention, asset-forth the appended claims. As appearing herein, the term “workvehicle” includes all parts of a work vehicle or work machine. Thus, inimplementations in which a boom assembly terminating in an implement isattached to the chassis of a work vehicle, the term “work vehicle”encompasses both the chassis and the boom assembly, as well as theimplement or tool mounted to the terminal end of the boom assembly.

Overview

The following describes work vehicle joystick systems incorporatingmagnetorheological fluid (MRF) devices or subsystems, which providetactile feedback indicative of monitored operational parameters or“machine states” of work vehicles. During work vehicle operation, thebelow-described work vehicle MRF joystick system receives sensor dataindicative of at least one monitored parameter of a given work vehicle;and selectively vary an MRF resistance force impeding joystick movementin at least one degree of freedom (DOF) based, at least in part, onjoystick position and variations in the monitored parameter. In sodoing, the work vehicle MRF joystick system provides work vehicleoperators with tactile feedback indicative of the current state ormagnitude of the monitored operational parameter or machine state. Asthe tactile feedback is provided through the joystick device itself,this information is conveyed to the operator in a highly intuitive,rapid manner and without requiring the operator to avert visualattention from the work task at hand. Further, in at least someembodiments, the tactile feedback provided through the below-describedjoystick devices may help guide or influence operator control inputs topromote smooth or non-abrupt work vehicle operation, to increaseuniformity between operator expectations and work vehicle performance,and to provide similar benefits. Overall operator satisfaction levelsand work vehicle efficiency may be improved as a result.

Embodiments of the work vehicle MRF joystick system include a processingsub-system or “controller architecture,” which is coupled to an MRFdamper or an MRF joystick resistance mechanism; that is, a mechanism ordevice containing a magnetorheological fluid and capable of modifyingthe rheology (viscosity) of the fluid through variations in the strengthof an electromagnetic (EM) field to provide controlled adjustments tothe resistive force impeding joystick motion in at least one DOF. Thisresistive force is referred to below as an “MRF resistance force,” whilethe degree to which an MRF resistance force impedes joystick motion in aparticular direction or combination of directions is referred to as the“joystick stiffness.” The MRF joystick resistance mechanism may becommanded by the controller architecture to apply various differentresistive effects selectively impeding joystick rotation or otherjoystick motion in any given direction, over any given range of travelof the joystick, and through the application of varying magnitudes ofresistive force. For example, embodiments of the MRF joystick system mayprogressively increase joystick stiffness in proportion to changes incertain monitored parameters; e.g., in embodiment, and as discussed indetail below, the controller architecture may command the MRF joystickresistance mechanism to increase the MRF resistance force (and,therefore, joystick stiffness) as a monitored parameter, such as amaterial load, a hydraulic pressure, or work vehicle ground speed,increases in magnitude. Additionally or alternatively, embodiments ofthe MRF joystick system may generate other MRF-applied effects, such asdetent or pulsating effects, briefly impeding joystick motion as amonitored parameter surpasses predetermined thresholds. Further,embodiments of the MRF joystick control system may be capable ofincreasing joystick stiffness in a single DOF or, instead, ofindependently increasing joystick stiffness in multiple DOFs. Forexample, in implementations which a joystick is rotatable about twoperpendicular axes, the MRF joystick resistance mechanism may be capableof independently vary joystick stiffnesses about the two rotational axesof the joystick.

The work vehicle MRF joystick system provides a high level offlexibility, both from design and customization standpoints. Regardingdesign flexibility, the MRF joystick system can be configured to varyjoystick stiffness in response to a wide range of monitored parameterspertaining to work vehicles of varying types employed in construction,agriculture, mining, and forestry industries. A non-exhaustive list ofsuch monitored parameters includes work vehicle ground speed(particularly in the case of joystick-steered work vehicles), theproximity of movable work vehicle components (e.g., boom assembly jointsor hydraulic cylinders) to motion stops, and various loads placed on awork vehicle. In the latter regard, embodiments of the MRF joysticksystem may monitor, and selectively vary the MRF joystick resistanceforce based upon, material loads carried by the work vehicle, such asthe fill load of a bucket attached to a boom assembly. Similarly, inembodiments, the MRF resistance force and joystick stiffness in at leastone DOF may be varied based on hydraulic pressures included withinelectrohydraulic (EH) actuation system utilized to animate movableimplements, such as moveable blades (in the case of, for example dozersand motor graders) and implements attached to boom assemblies (in thecase of, for example, excavators, feller bunchers, tractors equippedwith front end loader (FEL) attachments, wheel loaders, backhoes, andexcavators). In still other embodiments, the MRF resistance force andjoystick stiffness may be varied as a function of other loads placed ona work vehicle, such as the load placed on the primary engine of a workvehicle. In such embodiments, the controller architecture mayprogressively increase the MRF resistance force inhibiting joystickmovement as the monitored parameter increases, provide tactile cues(e.g., an MRF-applied feel detent or pulsating effect) when a monitoredparameter surpasses a preset threshold, and/or otherwise manipulate theMRF resistance force to provide tactile feedback indicative of themonitored parameter.

In further embodiments, the work vehicle MRF joystick system may varythe MRF resistance force to emulate legacy mechanical control schemes inwhich a joystick is mechanically linked to an actuated component of thework vehicle, such as a pilot valve included in an EH actuation system.For example, in certain implementations, the controller architecture mayutilize sensor data to monitor the pressure conditions or valvepositions of an EH actuation system and generate certain resistanceeffects (e.g., a brief pulse of resistance or feel detent) simulatingthe tactile feedback inherently provided by legacy systems in which amechanical connection is provided between an actuated component, such asa pilot valve, and a joystick device. This, in turn, may provide anoperator with familiar tactile cues regarding the operational status ofthe EH system (e.g., when pilot valve lift-off or cracking occurs) inthe context of an EH control scheme as opposed to a purely mechanicaljoystick control scheme. Stated differently, the controller architecturemay command the MRF joystick resistance mechanism to selectively varythe MRF resistance force in a manner providing tactile feedbackindicating when the pilot valve initially opens during usage of the EHactuation system.

In still other embodiments, the MRF joystick system may vary the MRFresistance force impeding joystick motion as a function of a currentmonitored machine parameter, such as a current steering angle or groundspeed, relative to an operator input command received via a joystickdevice. As a more specific example, embodiments of the MRF joysticksystem may progressively increase the MRF resistance force or joystickstiffness to should an operator attempt to rotate (or otherwise move) ajoystick in a manner that, if allowed to continue unimpeded, wouldresult in an abrupt change in work vehicle motion. Examples of such workvehicle motions (any or all of which may be controlled utilizing ajoystick in embodiments) include work vehicle heading or steering angle,work vehicle ground speed, and movement of a boom-mounted implement.Such an approach of increasing the MRF resistance force inhibitingjoystick motion when joystick inputs would result in abrupt work vehiclemotions is referred to herein as “trajectory shaping,” as discussed morefully below. Trajectory shaping by selective variations in joystickstiffness may encourage operator joystick movements bringing aboutrelatively seamless or smooth transitions in work vehicle motions.Additionally, such an approach allows operator intent to be confirmed,in passive sense, when an operator exerts sufficient force on thejoystick to overcome the increased MRF resistance force to, for example,abruptly change the steering angle or ground speed of the work vehicle.

As indicated above, embodiments of the work vehicle MRF joystick systemcan also provide a relatively high degree of customization flexibilityby, for example, enabling the below-described MRF resistance effects tobe tailored to operator preference. In this regard, an operator may bepermitted to adjust the intensity of the MRF resistance effect topreference in embodiments; or, perhaps, to selectively activate ordeactivate a given MRF resistance effect altogether. In other instances,the MRF joystick system may permit an operator to program the MRFresistance effects by, for example, selecting the particular monitoredparameter or parameters upon joystick stiffness is varied. Suchpersonalization or customization settings may be stored in memory andassociated with a particular operator in embodiments. Upon work vehiclestartup, or at another appropriate juncture during work vehicleoperation, the MRF customization settings may then be recalled basedupon the identity of the current operator (e.g., as determined by entryof an operator-specific pin when first logging into the work vehicle oras otherwise ascertained) and then applied as appropriate.

An example embodiment of a work vehicle MRF joystick system will now bedescribed in conjunction with FIGS. 1-5. In the below-described exampleembodiment, the MRF joystick system is principally discussed in thecontext of a particular type of work vehicle, namely, an excavator.Additionally, in the following example, the MRF joystick system includestwo joystick devices, which each have a joystick rotatable about twoperpendicular axes and which are utilized to control movement of theexcavator boom assembly and the implement or tool (e.g., bucket,grapple, or hydraulic hammer) attached thereto. The following examplenotwithstanding, the MRF joystick system may include a greater or lessernumber of joysticks in further embodiments, with each joystick devicemovable in any number of DOFs and along any suitable motion pattern orrange; e.g., in alternative implementations, a given joystick device maybe rotatable about a single axis or, perhaps, movable along a limited(e.g., H-shaped) track or motion pattern. Moreover, the below-describedMRF joystick system can be deployed on wide range of work vehiclesincluding joystick-controlled functions, additional examples of whichare discussed below in connection with FIG. 6.

Example MRF Joystick System Providing Machine State Feedback

Referring initially to FIG. 1, an example work vehicle (here, anexcavator 20) equipped with a work vehicle MRF joystick system 22 ispresented. In addition to the MRF joystick system 22, the excavator 20includes a boom assembly 24 terminating in a tool or implement, such abucket 26. Various other implements can be interchanged with the bucket26 and attached to the terminal end of the boom assembly 24 including,for example, other buckets, grapples, and hydraulic hammers. Theexcavator 20 features a body or chassis 28, a tracked undercarriage 30supporting the chassis 28, and a cabin 32 located at forward portion ofthe chassis 28 and enclosing an operator station. The excavator boomassembly 24 extends from the chassis 28 and contains, as principalstructural components, an inner or proximal boom 34 (hereafter, “thehoist boom 34”), an outer or distal boom 36 (hereafter, “the dipperstick36”), and a number of hydraulic cylinders 38, 40, 42. The hydrauliccylinders 38, 40, 42 include, in turn, two hoist cylinders 38, adipperstick cylinder 40, and a bucket cylinder 42. Extension andretraction of the hoist cylinders 38 rotates the hoist boom 34 about afirst pivot joint at which the hoist boom 34 is joined to the excavatorchassis 28, here at location adjacent (to the right of) the cabin 32.Extension and retraction of the dipperstick cylinder 40 rotates thedipperstick 36 about a second pivot joint at which the dipperstick 36 isjoined to the hoist boom 34. Finally, extension and retraction of thebucket cylinder 42 rotates or “curls” the excavator bucket 26 about athird pivot joint at which the bucket 26 is joined to the dipperstick36.

The hydraulic cylinders 38, 40, 42 are included in an electrohydraulic(EH) actuation system 44, which is encompassed by a box 46 entitled“actuators for joystick-controlled functions” in FIG. 1. Movements ofthe excavator boom assembly 24 are controlled utilizing at least onejoystick located within the excavator cabin 32 and included in the MRFjoystick system 22. Specifically, an operator may utilize the joystickor joysticks included in the MRF joystick system 22 to control theextension and retraction of the hydraulic cylinders 38, 40, 42, as wellas to control the swing action of the boom assembly 24 via rotation ofthe excavator chassis 28 relative to the tracked undercarriage 30. Thedepicted EH actuation system 44 also contains various othernon-illustrated hydraulic components, which may include flow lines(e.g., flexible hoses), check or relief valves, pumps, a, fittings,filters, and the like. Additionally, the EH actuation system 44 containselectronic valve actuators and flow control valves, such as spool-typemulti-way valves, which can be modulated to regulate the flow ofpressurized hydraulic fluid to and from the hydraulic cylinders 38, 40,42. This stated, the particular construction or architecture of the EHactuation system 44 is largely inconsequential to embodiments of thepresent disclosure, providing that the below-described controllerarchitecture 50 is capable of controlling movement of the boom assembly24 via commands transmitted to selected ones of the actuators 46effectuating the joystick controlled functions of the excavator 20.

As schematically illustrated in an upper left portion of FIG. 1, thework vehicle MRF joystick system 22 contains one or more MRF joystickdevices 52, 54. As appearing herein, the term “MRF joystick device”refers to an operator input device including at least one joystick orcontrol lever, the movement of which can be impeded by a variableresistance force or “stiffness force” applied utilizing an MRF joystickresistance mechanism of the type described herein. While one such MRFjoystick device 52 is schematically shown in FIG. 1 for clarity, the MRFjoystick system 22 can include any practical number of joystick devices,as indicated by symbol 58. In the case of the example excavator 20, theMRF joystick system 22 will typically include two joystick devices;e.g., joystick devices 52, 54 described below in connection with FIG. 2.The manner in which two such joystick devices 52, 54 may be utilized tocontrol movement of the excavator boom assembly 24 is further discussedbelow. First, however, a general discussion of the joystick device 52,as schematically illustrated in FIG. 1, is provided to establish ageneral framework in which embodiments of the present disclosure may bebetter understood.

As schematically illustrated in FIG. 1, the MRF joystick device 52includes a joystick 60 mounted to a lower support structure or basehousing 62. The joystick 60 is movable relative to the base housing 62in at least one DOF and may be rotatable relative to the base housing 62about one or more axes. In the depicted embodiment, and as indicated byarrows 64, the joystick 60 of the MRF joystick device 52 is rotatablerelative to the base housing 62 about two perpendicular axes and will bedescribed below as such. The MRF joystick device 52 includes one or morejoystick position sensors 66 for monitoring the current position andmovement of the joystick 60 relative to the base housing 62. Variousother components 68 may also be included in the MRF joystick device 52including buttons, dials, switches, or other manual input features,which may be located on the joystick 60 itself, located on the basehousing 62, or a combination thereof. Spring elements (gas ormechanical), magnets, or fluid dampers may be incorporated into thejoystick device 52 to provide a desired rate of return to a homeposition of the joystick, as well as to fine-tune the desired feel ofthe joystick 60 perceived by an operator when interacting with the MRFjoystick device 52. Such mechanisms are referred to herein as “joystickbias mechanisms” and may be contained within in the MRF joystick device52 when having a self-centering design. In more complex components,various other components (e.g., potentially including one or moreartificial force feedback (AFF) motors) can also be incorporated intothe MRF joystick device 52. In other implementations, such componentsmay be omitted from the MRF joystick device 52.

An MRF joystick resistance mechanism 56 is at least partially integratedinto the base housing 62 of the MRF joystick device 52. The MRF joystickresistance mechanism 56 (and the other MRF joystick resistancemechanisms mentioned in this document) may also alternatively bereferred to as an “MRF damper,” as an “MRF brake device,” or as simplyan “MRF device” or “MRF mechanism.” The MRF joystick resistancemechanism 56 can be controlled to adjust the MRF resistance force and,therefore, joystick stiffness resisting joystick motion relative to thebase housing 62 in at least one DOF. During operation of the MRFjoystick system 22, the controller architecture 50 may selectivelycommand the MRF joystick resistance mechanism 56 to increase thejoystick stiffness impeding joystick rotation about a particular axis orcombination of axes. As discussed more fully below, the controllerarchitecture 50 may command the MRF joystick resistance mechanism 56 toincrease joystick stiffness, when appropriate to perform any one of anumber of enhanced joystick functionalities, by increasing the strengthof an EM field in which a magnetorheological fluid contained in the MRFjoystick resistance mechanism 56 is at least partially immersed. Ageneralized example of one manner in which the MRF joystick resistancemechanism 56 may be realized is described below in connection with FIGS.3 and 4.

The excavator 20 is further equipped with any number of onboard sensors70. Such sensors 70 may include sensors contained in an obstacledetection system, which may be integrated into the excavator 20 inembodiments. The non-joystick input sensors 70 may further include anynumber and type of boom assembly sensors 72, such as boom assemblytracking sensors suitable for tracking the position and movement of theexcavator boom assembly 24. Such sensors can include rotary or linearvariable displacement transducers integrated into excavator boomassembly 24 in embodiments. For example, in one possible implementation,rotary position sensors may be integrated into the pivot joints of theboom assembly 24; and the angular displacement readings captured by therotary position sensors, taken in conjunction with known dimensions ofthe boom assembly 24 (as recalled from the memory 48), may be utilizedto track the posture and position of the boom assembly 24 (including thebucket 26) in three dimensional space. In other instances, the extensionand reaction of the hydraulic cylinders 38, 40, 42 may be measured(e.g., utilizing linear variable displacement transducers) and utilizedto calculate the current posture and positioning of the excavator boomassembly 24. Other sensor inputs can also be considered by thecontroller architecture 50 in addition or lieu of the aforementionedsensor readings, such as inertia-based sensor readings; e.g., ascaptured by inertia sensors, such as MEMS gyroscopes, accelerometers,and possibly magnetometers packaged as IMUs, which are affixed to theexcavator 20 at various locations. For example, IMUs can be affixed tothe excavator chassis 28 and one or more locations (different linkages)of the excavator boom assembly 24. Vision systems capable of tracking ofthe excavation implement or performing other functions related to theoperation of the excavator 20 may also be included in the onboard boardsensors 70 when useful in performing the functions described below.

One or more load measurement sensors, such as weight- or strain-basedsensors (e.g., load cells), may further be included in the non joysticksensor inputs 70 in at least some implementations of the work vehicleMRF joystick system 22. In embodiments, such load measurement sensorsmay be utilized to directly measure the load carried by the bucket 26(generally, a “load-moving implement” or “load-carrying implement”) atany given time during excavator operation. The load measurement sensorscan also measure other parameters (e.g., one or more hydraulic pressureswithin the EH actuation system 44) indicative of the load carried by theboom assembly 24 in embodiments. In other realizations, the MRF joysticksystem 22 may be integrated into a work vehicle having a bed or tank fortransporting a material, such as the bed of an articulated dump truck.In this latter case, the load measurement sensors included in thesensors 70 may assume the form of payload weighing sensors capable ofweighing or approximating the weight of material carried within the bedor tank of the work vehicle at any particular juncture in time.

In embodiments, the work vehicle sensors 70 may further include a numberof vehicle motion data sources 74. The vehicle motion data sources 74can include any sensors or data sources providing information pertainingto changes in the position, speed, heading, or orientation of theexcavator 20. Again, MEMS gyroscopes, accelerometers, and possiblymagnetometers packaged IMUs can be utilized to detect and measure suchchanges. Inclinometers or similar sensors may be employed to monitor theorientation of the excavator chassis 28 or portions of the boom assembly24 relative to gravity in embodiments. The vehicle motion data sources74 may further include Global Navigation Satellite System (GNSS)modules, such as Global Positioning System (GPS) modules, for monitoringexcavator position and motion states. In embodiments, the vehicle motiondata sources 74 may also include sensors from which the rotational rateof the undercarriage tracks may be calculated, electronic compasses formonitoring heading, and other such sensors. The vehicle motion datasources 74 can also include various sensors for monitoring the motionand position of the boom assembly 24 and the bucket 26, including MEMSdevices integrated into the boom assembly 24 (as previously noted),transducers for measuring angular displacements at the pin joints of theboom assembly, transducers for measuring the stroke of the hydrauliccylinders 38, 40, 42, and the like.

Embodiments of the MRF joystick system 22 may further include any numberof other non-joystick components 76 in addition to those previouslydescribed. Such additional non-joystick components 76 may include anoperator interface 78 (distinct from the MRF joystick device 52), adisplay device 80 located in the excavator cabin 32, and various othertypes of non-joystick sensors 82. The operator interface 78, inparticular, can include any number and type of non joystick inputdevices for receiving operator input, such as buttons, switches, knobs,and similar manual inputs external to the MRF joystick device 52. Suchinput devices included in the operator interface 78 can also includecursor-type input devices, such as a trackball or joystick, forinteracting with a graphical user interface (GUI) generated on thedisplay device 80. The display device 80 may be located within the cabin32 and may assume the form of any image-generating device on whichvisual alerts and other information may be visually presented. Thedisplay device 80 may also generate a GUI for receiving operator inputor may include other inputs (e.g., buttons or switches) for receivingoperator input, which may be pertinent to the controller architecture 50when performing the below-described processes. In certain instances, thedisplay device 80 may also have touch input capabilities.

Finally, the MRF joystick system 22 can include various othernon-joystick sensors 82, which provide the controller architecture 50with data inputs utilized in carrying-out the below-described processes.For example, the non-joystick sensors 82 can include sensors forautomatically determining the type of implement currently attached tothe excavator 20 (or other work vehicle) in at least someimplementations when this information is considered by the controllerarchitecture 50 in determining when to increase joystick stiffness toperform certain enhanced joystick functions described herein; e.g., suchsensors 82 may determine a particular implement type currently attachedto the excavator 20 by sensing a tag (e.g., a radio frequencyidentification tag) or reading other identifying information present onthe implement, by visual analysis of a camera feed capturing theimplement, or utilizing any other technique. In other instances, anoperator may simply enter information selecting the implement typecurrently attached to the boom assembly 24 by, for example, interactingwith a GUI generated on the display device 80. In still other instances,such other non-joystick sensors 82 may include sensors or camerascapable of determining when an operator grasps or other contacts thejoystick 60. In other embodiments, such sensors may not be contained inthe MRF joystick system 22.

As further schematically depicted in FIG. 1, the controller architecture50 is associated with a memory 48 and may communicate with the variousillustrated components over any number of wired data connections,wireless data connections, or any combination thereof; e.g., asgenerically illustrated, the controller architecture 50 may receive datafrom various components over a centralized vehicle or a controller areanetwork (CAN) bus 84. The term “controller architecture,” as appearingherein, is utilized in a non-limiting sense to generally refer to theprocessing subsystem of a work vehicle MRF joystick system, such as theexample MRF joystick system 22. Accordingly, the controller architecture50 can encompass or may be associated with any practical number ofprocessors, individual controllers, computer-readable memories, powersupplies, storage devices, interface cards, and other standardizedcomponents. In many instances, the controller architecture 50 mayinclude a local controller directly associated with the joystickinterface and other controllers located within the operator stationenclosed by the cabin 32, with the local controller communicating withother controllers onboard the excavator 20 as needed. The controllerarchitecture 50 may also include or cooperate with any number offirmware and software programs or computer-readable instructionsdesigned to carry-out the various process tasks, calculations, andcontrol functions described herein. Such computer-readable instructionsmay be stored within a non-volatile sector of the memory 48 associatedwith (accessible to) the controller architecture 50. While genericallyillustrated in FIG. 1 as a single block, the memory 48 can encompass anynumber and type of storage media suitable for storing computer-readablecode or instructions, as well as other data utilized to support theoperation of the MRF joystick system 22. The memory 48 may be integratedinto the controller architecture 50 in embodiments as, for example, asystem-in-package, a system-on-a-chip, or another type ofmicroelectronic package or module.

Discussing the joystick configuration or layout of the excavator 20 ingreater detail, the number of joystick devices included in the MRFjoystick system 22, and the structural aspects and function of suchjoysticks, will vary amongst embodiments. As previously mentioned,although only a single joystick device 52 is schematically shown in FIG.1, the MRF joystick system 22 will typically two joystick devices 52, 54supporting excavator boom assembly control. Further illustrating thispoint, FIG. 2 provides a perspective view from within the excavatorcabin 32 and depicting two MRF joystick devices 52, 54 suitably includedin embodiments of the MRF joystick system 22. As can be seen, the MRFjoystick devices 52, 54 are positioned on opposing sides of an operatorseat 86 such that an operator, using both hands, can concurrentlymanipulate the left MRF joystick device 52 and the right joystick device54 with relative ease. Carrying forward the reference numeralsintroduced above in connection with FIG. 1, each joystick device 52, 54includes a joystick 60 mounted to a lower support structure or basehousing 62 for rotation relative to the base housing 62 about twoperpendicular axes. The joystick devices 52, 54 also each include aflexible cover or boot 88 joined between a lower portion of thejoysticks 60 and their respective base housings 62. Additional joystickinputs are also provided on each joystick 60 in the form ofthumb-accessible buttons and, perhaps, as other non-illustrated manualinputs (e.g., buttons, dials, and or switches) provided on the basehousings 62. Other notable features of the excavator 20 shown in FIG. 2include the previously-mentioned display device 80 and pedal/controllever mechanisms 90, 92 for controlling the respective movement of theright and left tracks of the tracked undercarriage 30.

Different control schemes can be utilized to translate movement of thejoysticks 60 included in the joystick devices 52, 54 to correspondingmovement of the excavator boom assembly 24. In many instances, theexcavator 20 will support boom assembly control in either (and oftenallow switching between) a “backhoe control” or “SAE control” patternand an “International Standard Organization” or “ISO” control pattern.In the case of the backhoe control pattern, movement of the leftjoystick 60 to the operator's left (arrow 94) swings the excavator boomassembly 24 in a leftward direction (corresponding to counter-clockwiserotation of the chassis 28 relative to the tracked undercarriage 30),movement of the left joystick 60 to the operator's right (arrow 96)swings the boom assembly 24 in a rightward direction (corresponding toclockwise rotation of the chassis 28 relative to the trackedundercarriage 30), movement of the left joystick 60 in a forwarddirection (arrow 98) lowers the hoist boom 34, and movement of the leftjoystick 60 in an aft or rearward direction (arrow 100) raises the hoistboom 34. Also, in the case of the backhoe control pattern, movement ofthe right joystick 60 to the left (arrow 102) curls the bucket 26inwardly, movement of the right joystick 60 to the right (arrow 104)uncurls or “opens” the bucket 26, movement of the right joystick 60 in aforward direction (arrow 106) rotates the dipperstick 36 outwardly, andmovement of the right joystick 60 in an aft or rearward direction (arrow108) rotates the dipperstick 36 inwardly. Comparatively, in the case ofan ISO control pattern, the joystick motions for the swing commands andthe bucket curl commands are unchanged, while the joystick mappings ofthe hoist boom and dipperstick are reversed. Thus, in the ISO controlpattern, forward and aft movement of the left joystick 60 controls thedipperstick rotation in the previously described manner, while forwardand aft movement of the right joystick 60 controls motion (raising andlowering) of the hoist boom 34 in the manner described above.

Turning now to FIGS. 3 and 4, an example construction of the MRFjoystick device 52 and the MRF joystick resistance mechanism 56 isrepresented by two simplified cross-sectional schematics. While thesedrawing figures illustrate a single MRF joystick device (i.e., the MRFjoystick device 52), the following description is equally applicable tothe other MRF joystick device 54 included in the example MRF joysticksystem 22. The following description is provided by way of non-limitingexample only, noting that numerous different joystick designsincorporating or functionally cooperating with MRF joystick resistancemechanisms are possible. The particular composition of themagnetorheological fluid largely is also inconsequential to embodimentsof the present disclosure, providing that meaningful variations in therheological properties (viscosity) of the magnetorheological fluid occurin conjunction with controlled variations in EM field strength, asdescribed below. For completeness, however, is noted that onemagnetorheological fluid composition well-suited for usage inembodiments of the present disclosure contains magnetically-permeable(e.g., carbonyl iron) particles dispersed in a carrier fluid, which ispredominately composed of an oil or an alcohol (e.g., glycol) by weight.Such magnetically-permeable particles may have an average diameter (orother maximum cross-sectional dimension if the particles possess anon-spherical (e.g., oblong) shape) in the micron range; e.g., in oneembodiment, spherical magnetically-permeable particles are used havingan average diameter between one and ten microns. Various otheradditives, such as dispersants or thinners, may also be included in themagnetorheological fluid to fine-tune the properties thereof.

Referring now to the example joystick construction shown in FIGS. 3 and4, and again carrying forward the previously-introduced referencenumerals as appropriate, the MRF joystick device 52 includes a joystick60 having at least two distinct portions or structural regions: an upperhandle 110 (only a simplified, lower portion of which is shown in thedrawing figures) and a lower, generally spherical base portion 112(hereafter, the “generally spherical base 112”). The generally sphericalbase 112 of the joystick 60 is captured between two walls 114, 116 ofthe base housing 62, which may extend substantially parallel to oneanother to form an upper portion of the base housing 62.Vertically-aligned central openings are provided through the housingwalls 114, 116, with the respective diameters of the central openingsdimensioned to be less than the diameter of the generally spherical base112. The spacing or vertical offset between the walls 114, 116 isfurther selected such that the bulk of generally spherical base 112 iscaptured between the vertically-spaced housing walls 114, 116 to form aball-and-socket type joint. This permits rotation of the joystick 60relative to the base housing 62 about two perpendicular axes, whichcorrespond to the X- and Y-axes of a coordinate legend 118 appearing inFIGS. 3 and 4; while generally preventing translational movement of thejoystick 60 along the X-, Y-, and Z-axes of the coordinate legend 118.In further embodiments, various other mechanical arrangements can beemployed to mount a joystick to a base housing, while allowing rotationof the joystick about two perpendicular axis, such as a gimbalarrangement. In less complex embodiments, a pivot or pin joint may beprovided to permit rotation of the joystick 60 relative to the basehousing 62 about a single axis.

The joystick 60 of the MRF joystick device 52 further includes a stingeror lower joystick extension 120, which projects from the generallyspherical base 112 in a direction opposite the joystick handle 110. Thelower joystick extension 120 is coupled to a static attachment point ofthe base housing 62 by a single centering or return spring 124 in theillustrated schematic; here noting that such an arrangement issimplified for the purposes of illustration and more complex springreturn arrangements (or other joystick biasing mechanisms, if present)will typically be employed in actual embodiments of the MRF joystickdevice 52. When the joystick 60 is displaced from the neutral or homeposition shown in FIG. 3, the return spring 124 deflects as shown inFIG. 4 to urge return of the joystick 60 to the home position (FIG. 3).Consequently, as an example, after rotation into the position shown inFIG. 4, the joystick 60 will return to the neutral or home positionshown in FIG. 3 under the influence of the return spring 124 should thework vehicle operator subsequently release the joystick handle 110. Inother embodiments, the MRF joystick device 52 may not be self-centeringand may, instead, assume the form a friction-hold joystick remaining ata particular position absent an operator-applied force moving thejoystick from the position.

The example MRF joystick resistance mechanism 56 includes a first andsecond MRF cylinders 126, 128 shown in FIGS. 3 and 4, respectively. Thefirst MRF cylinder 126 (FIG. 3) is mechanically joined between the lowerjoystick extension 120 and a partially-shown, static attachment point orinfrastructure feature 130 of the base housing 62. Similarly, the secondMRF cylinder 128 (FIG. 4) is mechanically joined between the lowerjoystick extension 120 and a static attachment point 132 of the basehousing 62, with the MRF cylinder 128 rotated relative to the MRFcylinder 126 by approximately 90 degrees about the Z-axis of thecoordinate legend 118. Due to this structural configuration, the MRFcylinder 126 (FIG. 3) is controllable to selectively resist rotation ofthe joystick 60 about the X-axis of coordinate legend 118, while the MRFcylinder 128 (FIG. 4) is controllable to selectively resist rotation ofthe joystick 60 about the Y-axis of coordinate legend 118. Additionally,both MRF cylinders 126, 128 can be jointly controlled to selectivelyresist rotation of the joystick 60 about any axis falling between the X-and Y-axes and extending within the X-Y plane. In other embodiments, adifferent MRF cylinder configuration may be utilized and include agreater or lesser number of MRF cylinders; e.g., in implementations inwhich it is desirable to selectively resist rotation of joystick 60about only the X-axis or only the Y-axis, or in implementations in whichjoystick 60 is only rotatable about a single axis, a single MRF cylinderor a pair of antagonistic cylinders may be employed. Finally, althoughnot shown in the simplified schematics, any number of additionalcomponents can be included in or associated with the MRF cylinders 126,128 in further implementations. Such additional components may includesensors for monitoring the stroke of the cylinders 126, 128 if desirablyknown to, for example, track joystick position in lieu of thebelow-described joystick sensors 182, 184.

The MRF cylinders 126, 128 each include a cylinder body 134 to which apiston 138, 140 is slidably mounted. Each cylinder body 134 contains acylindrical cavity or bore 136 in which a head 138 of one of the pistons138, 140 is mounted for translational movement along the longitudinalaxis or centerline of the cylinder body 134. About its outer periphery,each piston head 138 is fitted with one or more dynamic seals (e.g.,O-rings) to sealingly engaging the interior surfaces of the cylinderbody 134, thereby separating the bore 136 into two antagonisticvariable-volume hydraulic chambers. The pistons 138, 140 also eachinclude an elongated piston rod 140, which projects from the piston head138 toward the lower joystick extension 120 of the joystick 60. Thepiston rod 140 extends through an end cap 142 affixed over the open endof the cylinder body 134 (again, engaging any number of seals) forattachment to the lower joystick extension 120 at a joystick attachmentpoint 144. In the illustrated example, the joystick attachment points144 assume the form of pin or pivot joints; however, in otherembodiments, more complex joints (e.g., spherical joints) may beemployed to form this mechanical coupling. Opposite the joystickattachment points 144, the opposing end of the MRF cylinders 126, 128are mounted to the respective static attachment points 130, 132 viaspherical joints 145. Finally, hydraulic ports 146, 148 are furtherprovided in opposing end portions of each MRF cylinder 126, 128 to allowthe inflow and outflow of magnetorheological fluid in conjunction withtranslational movement or stroking of the pistons 138, 140 along therespective longitudinal axes of the MRF cylinders 126, 128.

The MRF cylinders 126, 128 are fluidly interconnected with correspondingMRF values 150, 152, respectively, via flow line connections 178, 180.As is the case with the MRF cylinders 126, 128, the MRF valves 150, 152are presented as identical in the illustrated example, but may vary infurther implementations. Although referred to as “valves” by commonterminology (considering, in particular, that the MRF valves 150, 152function to control magnetorheological fluid flow), it will be observedthat the MRF valves 150, 152 lack valve elements and other movingmechanical parts in the instant example. As a beneficial corollary, theMRF valves 150, 152 provide fail safe operation in that, in the unlikelyevent of MRF valve failure, magnetorheological fluid flow is stillpermitted through the MRF valves 150, 152 with relatively littleresistance. Consequently, should either or both of the MRF valves 150,152 fail for any reason, the ability of MRF joystick resistancemechanism 56 to apply resistance forces restricting or impeding joystickmotion may be compromised; however, the joystick 60 will remain freelyrotatable about the X- and Y-axes in a manner similar to a traditional,non-MRF joystick system, and the MRF joystick device 52 will remaincapable of controlling the excavator boom assembly 24 as typical.

In the depicted embodiment, the MRF valves 150, 152 each include a valvehousing 154, which contains end caps 156 affixed over opposing ends ofan elongated cylinder core 158. A generally annular or tubular flowpassage 160 extends around the cylinder core 158 and between two fluidports 162, 164, which are provided through the opposing end caps 156.The annular flow passage 160 is surrounded by (extends through) a numberof EM inductor coils 166 (hereafter, “EM coils 166”), which are woundaround paramagnetic holders 168 and interspersed with a number ofaxially- or longitudinally-spaced ferrite rings 170. A tubular shroud172 surrounds this assembly, while a number of leads are providedthrough the shroud 172 to facilitate electrical interconnection with thehoused EM coils 166. Two such leads, and the corresponding electricalconnections to a power supply and control source 177, are schematicallyrepresented in FIGS. 3 and 4 by lines 174, 176. As indicated by arrows179, the controller architecture 50 is operably coupled to the powersupply and control source 177 in a manner enabling the controllerarchitecture 50 to control the source 177 to vary the current suppliedto or the voltage applied across the EM coils 166 during operation ofthe MRF joystick system 22. This structural arrangement thus allows thecontroller architecture 50 to command or control the MRF joystickresistance mechanism 56 to vary the strength of an EM field generated bythe EM coils 166. The annular flow passage 160 extends through the EMcoils 166 (and may be substantially co-axial therewith) such that themagnetorheological fluid passes through the center the EM field when asthe magnetorheological fluid is conducted through the MRF valves 150,152.

The fluid ports 162, 164 of the MRF valves 150, 152 are fluidlyconnected to the ports 146, 148 of the corresponding the MRF cylinders126, 128 by the above-mentioned conduits 178, 180, respectively. Theconduits 178, 180 may be, for example, lengths of flexible tubing havingsufficient slack to accommodate any movement of the MRF cylinders 126,128 occurring in conjunction with rotation of the joystick 60. Consider,in this regard, the example scenario of FIG. 4. In this example, anoperator has moved the joystick handle 110 in an operator inputdirection (indicated by arrow 185) such that the joystick 60 rotatesabout the Y-axis of coordinate legend 118 in a clockwise direction. Incombination with this joystick motion, the MRF cylinder 128 rotatesabout the spherical joint 145 to tilt slightly upward as shown. Also,along with this operator-controlled joystick motion, the piston 138, 140contained in the MRF cylinder 128 retracts such that the piston head 138moves to the left in FIG. 4 (toward the attachment point 132). Thetranslation movement of the piston 138, 140 forces magnetorheologicalfluid flow through the MRF valve 152 to accommodate the volumetricdecrease of the chamber on the left of the piston head 138 and thecorresponding volumetric increase of the chamber to the right of thepiston head 138. Consequently, at any point during such anoperator-controlled joystick rotation, the controller architecture 50can vary the current supplied to or the voltage across the EM coils 166to vary the force resisting magnetorheological fluid flow through theMRF valve 152 and thereby achieve a desired MRF resistance forceresisting further stroking of the piston 138, 140.

Given the responsiveness of MRF joystick resistance mechanism 56, thecontroller architecture 50 can control the MRF joystick resistancemechanism 56 to only briefly apply such an MRF resistance force, toincrease the strength of the MRF resistance force in a predefined manner(e.g., in a gradual or stepped manner) with increasing pistondisplacement, or to provide various other resistance effects (e.g., atactile detent or pulsating effect), as discussed in detail below. Thecontroller architecture 50 can likewise control the MRF joystickresistance mechanism 56 to selectively provided such resistance effectsas the piston 138, 140 included in the MRF valve 150 strokes inconjunction with rotation of the joystick 60 about the X-axis ofcoordinate legend 118. Moreover, the MRF joystick resistance mechanism56 may be capable of independently varying the EM field strengthgenerated by the EM coils 166 within the MRF valves 150, 152 to allowindependent control of the MRF resistance forces impeding joystickrotation about the X- and Y-axes of coordinate legend 118.

The MRF joystick device 52 may further contain one or more joystickposition sensors 182, 184 (e.g., optical or non-optical sensors ortransformers) for monitoring the position or movement of the joystick 60relative to the base housing 62. In the illustrated example,specifically, the MRF joystick device 52 includes a first joystickposition sensor 182 (FIG. 3) for monitoring rotation of the joystick 60about the X-axis of coordinate legend 118, and a second joystickposition sensor 184 (FIG. 4) for monitoring rotation of the joystick 60about the Y-axis of coordinate legend 118. The data connections betweenthe joystick position sensors 182, 184 and the controller architecture50 are represented by lines 186, 188, respectively. In furtherimplementations, the MRF joystick device 52 can include various othernon-illustrated components, as can the MRF joystick resistance mechanism56. Such components can include operator inputs and correspondingelectrical connections provided on the joystick 60 or the base housing62, AFF motors, and pressure and/or flow rate sensors included in theflow circuit of the MRF joystick resistance mechanism 56, asappropriate, to best suit a particular application or usage.

As previously emphasized, the above-described embodiment of the MRFjoystick device 52 is provided by way of non-limiting example only. Inalternative implementations, the construction of the joystick 60 candiffer in various respects. So too may the MRF joystick resistancemechanism 56 differ in further embodiments relative to the example shownin FIGS. 3 and 4, providing that the MRF joystick resistance mechanism56 is controllable by the controller architecture 50 to selectivelyapply a resistance force (through changes in the rheology of amagnetorheological fluid) impeding movement of a joystick relative to abase housing in at least one DOF. In further realizations, EM inductorcoils similar or identical to the EM coils 166 may be directlyintegrated into the MRF cylinders 126, 128 to provide the desiredcontrollable MRF resistance effect. In such realizations,magnetorheological fluid flow between the variable volume chamberswithin a given MRF cylinder 126, 128 may be permitted via the provisionof one or more orifices through the piston head 138, by providing anannulus or slight annular gap around the piston head 138 and theinterior surfaces of the cylinder body 134, or by providing flowpassages through the cylinder body 134 or sleeve itself. Advantageously,such a configuration may impart the MRF joystick resistance mechanismwith a relatively compact, integrated design. Comparatively, the usageof one or more external MRF valves, such as the MRF valves 150, 152(FIGS. 3 and 4), may facilitate cost-effective manufacture and allow theusage of commercially-available modular components in at least someinstances.

In still other implementations, the design of the MRF joystick devicemay permit the magnetorheological fluid to envelop and act directly upona lower portion of the joystick 60 itself, such as the spherical base112 in the case of the joystick 60, with EM coils positioned around thelower portion of the joystick and surrounding the magnetological fluidbody. In such embodiments, the spherical base 112 may be provided withribs, grooves, or similar topological features to promote displacementof the magnetorheological fluid in conjunction with joystick rotation,with energization of the EM coils increasing the viscosity of themagnetorheological fluid to impede fluid flow through restricted flowpassages provided about the spherical base 112 or, perhaps, due tosheering of the magnetorheological fluid in conjunction with joystickrotation. Various other designs are also possible in further embodimentsof the MRF joystick system 22.

Regardless of the particular design of the MRF joystick resistancemechanism 56, the usage of MRF technology to selectively generate avariable MRF resistance force or joystick stiffness impeding (resistingor preventing) targeted joystick motions provides several advantages. Asa primary advantage, the MRF joystick resistance mechanism 56 (and MRFjoystick resistance mechanism generally) are highly responsive and caneffectuate desired changes in EM field strength, in the rheology of themagnetorheological fluid, and ultimately in the MRF-applied joystickstiffness impeding joystick motions in highly abbreviated time periods;e.g., time periods on the order of 1 millisecond in certain instances.Correspondingly, the MRF joystick resistance mechanism 56 may enable theMRF resistance force to be removed (or at least greatly reduced) with anequal rapidity by quickly reducing current flow through the EM coils andallowing the rheology of the magnetorheological fluid (e.g., fluidviscosity) to revert to its normal, unstimulated state. The controllerarchitecture 50 can further control the MRF joystick resistancemechanism 56 to generate the MRF resistance force to have a continuousrange of strengths or intensities, within limits, through correspondingchanges in the strength of the EM field generated utilizing the EM coils166. Beneficially, the MRF joystick resistance mechanism 56 can providereliable, essentially noiseless operation over extended time periods.Additionally, the magnetorheological fluid can be formulated to benon-toxic in nature, such as when the magnetorheological fluid containscarbonyl iron-based particles dispersed in an alcohol-based or oil-basedcarrier fluid, as previously described. Finally, as a still furtheradvantage, the above-described configuration of the MRF joystickresistance mechanism 56 allows the MRF joystick system 22 to selectivelygenerate a first resistance force or joystick stiffness deterringjoystick rotation about a first axis (e.g., the X-axis of coordinatelegend 118 in FIGS. 3 and 4), while further selectively generating asecond resistance force or joystick stiffness deterring joystickrotation about a second axis (e.g., the Y-axis of coordinate legend 118)independently of the first resistance force (joystick stiffness); thatis, such that the first and second resistance forces have differentmagnitudes, as desired.

Advancing next to FIG. 5, presented is an example process 190 suitablycarried-out by the controller architecture 50 of the above-described MRFjoystick system 22 to vary one or more MRF resistance forces selectivelyimpeding joystick motion in a manner providing machine state feedbackpertaining to a work vehicle, such as the example excavator 20 describedabove in connection with FIGS. 1 and 2. The illustrated example process190 (hereafter, the “MRF machine state feedback process 190”) includes anumber of process STEPS 192, 194, 196, 198, 200, 202, 204, 206, each ofwhich is described, in turn, below. Depending upon the particular mannerin which the MRF machine state feedback process 190 is implemented, eachstep generically illustrated in FIG. 5 may entail a single process ormultiple sub-processes. Further, the steps illustrated in FIG. 5 anddescribed below are provided by way of non-limiting example only. Inalternative embodiments of the MRF machine state feedback process 190,additional process steps may be performed, certain steps may be omitted,and/or the illustrated process steps may be performed in alternativesequences.

The MRF machine state feedback process 190 commences at STEP 192 inresponse to the occurrence of a predetermined trigger event. Inembodiments, the trigger event can be startup of a work vehicle (e.g.,the excavator 20 shown in FIGS. 1 and 2) or, instead, entry of operatorinput requesting activation of a particular joystick feedback mode. Forexample, in embodiments, an operator may interact with a GUI generatedon the display device 80 to active a desired feedback mode as auser-selectable option, possibly selected from a list of user-selectableoptions. In such embodiments, such a GUI may also permit the operator toadjust the intensity or other aspects of the MRF resistance force topreference, to select the monitored parameter correlated to variationsin joystick stiffness, and/or to selectively deactivate such MRF-appliedvariations in joystick stiffness, as previously discussed. In furtherimplementations of the process 190, the MRF machine state feedbackprocess 190 may commence in response to a different trigger event, suchas detection of a pertinent mode of operation on behalf of the workvehicle; e.g., in embodiments in which the MRF resistance force isvaried in response to changes in work vehicle ground speed or to achievetrajectory shaping, as further discussed below, the MRF machine statefeedback process 190 may commence when the work vehicle is pilotedutilizing one or more MRF joystick devices or, perhaps, when the groundspeed of the work vehicle surpasses a predetermined threshold.Similarly, in embodiments in which the MRF resistance force is varied inresponse to changes in a monitored load, the process 190 may commencewhen a monitored load of the work vehicle surpasses a preset minimumthreshold value.

Following commencement of the MRF machine state feedback process 190,the controller architecture 50 progresses to STEP 194 and collects thepertinent data inputs subsequently utilized to determine the appropriatevariations in the MRF resistance force or forces resisting joystickmotion in one or more DOFs. The particular data inputs gathered duringSTEP 194 will vary in relation to the parameter or parameters correlatedto the variable joystick stiffness, as discussed more fully below inconnection with STEPS 204, 206 of the MRF machine state feedback process190. Generally, iterations of the process 190 may be performed at arelatively rapid rate such that the data inputs collected during STEP194 may reflect real-time or near real-time data provided by one or moresensors onboard the work vehicle, such as any of the sensors 70 of theabove-described example excavator 20. Stored data may also be recalledfrom memory (e.g., the memory 48 shown in FIG. 1) by the controllerarchitecture 50, as needed, to determine the appropriate MRF resistanceforce correlated to the monitored parameter or sensor data. For example,in embodiments, multi-dimensional lookup tables, characteristics orformulae, or a similar data structures may be recalled from the memory48 and utilized to determine the appropriate MRF resistance forceadjustments based upon the real-time data received from one or moresensors included within the onboard sensors 70. So too may any operatorpreference settings, such as desired MRF resistance force intensitysettings, be recalled from the memory 48 and considered during STEPS204, 206 of the process 190.

Next, at STEP 196 of the MRF machine state feedback process 190, thecontroller architecture 50 receives data indicative of the currentjoystick movement and position of the MRF joystick device (or devices)under consideration. In the case of the example excavator 20, thecontroller architecture 50 receives data from the joystick positionsensors 182, 184 contained in the MRF joystick devices 52, 54 regardingthe movement of the respective joysticks 60 included in the devices 52,54. Such data enables the controller architecture 50 to rapidly increaseor decrease the MRF resistance force inhibiting joystick movement (e.g.,joystick rotation about a particular axis) in correlation to the currentjoystick position and movement characteristics. This, in turn, enablesthe MRF resistance force to progressively increase, to progressivelydecrease, to be quickly applied, or to be quickly removed, as needed, togenerate the desired MRF resistance effects.

Progressing to STEP 202 of the MRF machine state feedback process 190,the controller architecture 50 determines whether joystick position orthe monitored machine state correlated to joystick stiffness has changedin a manner warranting variations in the currently-applied MRFresistance force and, therefore, the joystick stiffness resistingjoystick motion in a particular direction. If this is the case, thecontroller architecture 50 progresses to STEP 204 of the MRF machinestate feedback process 190, as further described below. Otherwise, thecontroller architecture 50 advances to STEP 200 and determines whetherthe current iteration of the MRF machine state feedback process 190should terminate; e.g., due to work vehicle shutdown, due to continuedinactivity of the joystick-controlled function for a predetermined timeperiod, or due to removal of the condition or trigger event in responseto which the process 190 initially commenced. If determining that theMRF machine state feedback process 190 should terminate at STEP 200, thecontroller architecture 50 progresses to STEP 202 of the process 190,the MRF machine state feedback process 190 terminates accordingly. Ifinstead determining that the process 190 should continue, the controllerarchitecture 50 returns to STEP 194 and the above-described processsteps repeat.

As previously indicated, the controller architecture 50 advances to STEP204 when determining that joystick position or the monitored machinestate correlated to MRF joystick stiffness has changed based upon thedata inputs collected during STEPS 194, 196 of the MRF machine statefeedback process 190. During STEP 204, the controller architecture 50determines the appropriate manner in which to vary the MRF resistanceforce to achieve a desired joystick stiffness indicative of themonitored machine state or parameter. The controller architecture 50then advances to STEP 206 and applies the newly-determined MRFresistance force by transmitting appropriate commands to the MRFjoystick resistance mechanism 56 to vary the rheology (viscosity) of theMRF fluid body (or bodies) in a manner achieving the desired resistanceeffect. As discussed throughout this document, such effects arecorrelated to joystick position and, thus, may be temporarily applied togenerate detent effects or pulsating effects; the MRF resistance forcemay be progressively increased or otherwise varied to substantiallymatch increases in a monitored parameter (e.g., a ground speed, acomponent position, a load, or a hydraulic pressure of the workvehicle); or the MRF resistance force may be lessened or removed whenappropriate based upon joystick movement and the state of the monitoredparameter. After application of the determined adjustments to the MRFresistance force inhibiting joystick motion in at least one DOF, thecontroller architecture 50 then progresses to STEP 200 and determineswhether the current iteration of the MRF machine state feedback process190 should terminate, as previously discussed. In this manner, thecontroller architecture 50 may repeatedly perform iterations of theprocess 190 to actively vary the MRF resistance force impeding orresisting joystick motion in at least one DOF, such as joystick rotationabout one or more axes, to provide a work vehicle operator with tactilefeedback indicative of a monitored parameter pertaining to work vehicleas the operator interacts with a MRF joystick device, such as MRFjoystick device 52 discussed above in connection with FIGS. 1-4.

Discussing now STEP 204 of the MRF machine state feedback process 190 ingreater detail, several example machine state parameters 208, 210, 212,214, 215 are identified for which the MRF joystick system 22 may providetactile feedback via selectively variations in the MRF stiffness forceor forces resisting joystick movement. The illustrated machine stateparameters 208, 210, 212, 214, 215 are provided by way of non-limitingexample only and are each described, in turn, below. Initiallyaddressing the parameter entitled “work vehicle load” (parameter 208,FIG. 5), embodiments of the work vehicle MRF joystick system 22 may varythe MRF force resistance inhibiting joystick movement as a function ofany particular load, which is placed on the work vehicle and which ismonitored (directly or indirectly) utilizing one or more sensors onboardthe work vehicle. In embodiments in which a work vehicle is equippedwith a movable implement, such as a movable blade or a boom-mountedimplement, the controller architecture 50 may estimate a load forceresisting movement of the implement in at least one direction andincrease the joystick stiffness (through continuous or stepwiseincreases in the MRF resistance force) as the variable load placed onthe work increases.

In embodiments, the monitored work vehicle load may be any variableforce resisting movement of a component of the work vehicle in somemanner. For example, the monitored load may be the mass or weight of amaterial weight borne by load-carrying component of the work vehicle;the term “load-carrying component” encompassing buckets, grapples, balespears, feller heads, lifts, and other such tools or implements commonlyattached to work vehicles and utilized to transport materials or objectsfrom one location to another. Such load forces resisting movement of amovable implement may also forces encountered during excavationoperations as, for example, hardened regions of earth or otherdifficult-to-displace regions are encountered by a tool (e.g., atrencher, a hydraulic hammer, or a bucket). In each of these scenarios,the controller architecture 50 may estimate the load resisting implementmovement in any given direction or combination of directions and thencommand the MRF joystick resistance mechanism 56 to vary the MRFresistance force accordingly; e.g., such that the MRF resistance forceinhibiting joystick movement increases in conjunction with increases inthe force resisting implement movement in a given direction. Similarly,in embodiments in which the work vehicle comprises a load-carryingreceptacle, such as a bucket, tank, or bed, the MRF joystick system mayincrease the MRF resistance force with as the weight of the materialheld within the load-carrying receptacle (herein, the “fill weight”)increases. Such increases the MRF resistance force may be implemented ina stepwise fashion or, instead, in a substantially continual fashion(over a given resistance range) such that, for example, the MRFresistance force progressively increases in substantial portion toincreases in the monitored load. In other implementations, differentMRF-applied tactile cues (e.g., feel detents) may be generated when aload placed on the work vehicle surpasses or becomes equivalent to apredetermined threshold, such as in the case of the below-describedtipoff assist function.

The above-described variations in the MRF resistance force can beaxis-specific or direction-specific in embodiments in which the MRFjoystick device is capable of rotational about perpendicular axes, suchas in the case of the joystick device 52 shown in FIGS. 1-4. Consider,for example, an example in which the MRF resistance force or joystickstiffness is varied in proportion to the fill load contained in thebucket of a wheel loader, such as the wheel loader 216 discussed belowin connection with FIG. 6. In this example, the controller architecture50 may selectively increase the MRF resistance force in response tojoystick rotations (as detected during STEP 196 of the process 190)moving the joystick in forward and aft directions to lower and raise theFEL bucket, respectively, while leaving joystick rotations about theopposing axis (moving the joystick handle to the left and right) curlingand uncurling the bucket unhindered. Similarly, in embodiments, onlyjoystick motions raising the FEL bucket may be impeded by an increasedMRF resistance force as the estimated bucket load increases to impart anoperator with an intuitive sense of the relatively heavy load carried bythe bucket. Axis-specific or direction-specific variations in MRFresistance force can also be applied based upon the work vehiclefunction controlled by the work vehicle. For example, in the case of awork vehicle equipped with a hinged boom assembly, such as the excavator20 shown in FIGS. 1-2, calculations may be carried-out by the controllerarchitecture 50 utilizing the current estimated position and posture ofthe hinged boom assembly to estimate the load placed on the boomassembly-mounted implement (e.g., the bucket 26) at a given moment oftime, based upon the boom assembly posture relative to the directiongravity; e.g., as monitored utilizing a MEMS gyroscope, an inclinometer,or a similar sensor onboard the work vehicle. Consequently, in suchinstances, the controller architecture 50 may generate MRF resistanceforces to selectively impede joystick movements raising the bucket 26load against gravity, while providing little to no MRF resistance forceimpediment to joystick inputs moving the bucket in a plane orthogonal tothe direction of gravity (e.g., by swinging the boom assembly 24) andproviding little to no impediment (or perhaps further reducing any MRFresistance force) to actions moving the bucket downwardly in thedirection of gravity.

In embodiments in which the work vehicle includes an EH actuationsystem, the MRF joystick system may increase the MRF resistance force inconjunction with variations in a circuit pressure within the EHactuation system. For example, with respect to the example excavator 20discussed above in connection with FIGS. 1 and 2, the controllerarchitecture 50 may monitor at least one pressure (or a pressuredifferential) within a flow circuit of the EH actuation system 44 andincrease an MRF resistance force inhibiting joystick motion in at leastone DOF in conjunction with increasing circuit pressures. In thisregard, the controller architecture 50 may independently vary the MRFresistance force impeding joystick motions controlling differenthydraulic cylinders based on, for example, the estimated pressure orload of the cylinders utilized to control the boom assembly; e.g., thecylinders 38, 40, 42 shown in FIG. 1 utilized to animate the excavatorboom assembly 24. For example, as the pressure supplied to the hydraulichoist cylinders 38 increases, so too may the controller architecture 50increase the MRF resistance force inhibiting joystick motions causingfurther pressure increases of the hydraulic fluid supplied to thecylinders 38; e.g., joystick motion causing further extension of thecylinders 38 raising the hoist boom 34 in instances in which the bucket26 is heavily loaded or, conversely, joystick motion causing retractionof the cylinders 38 lowering the hoist boom 34 in instances in which theend effector (e.g., a hydraulic hammer) attached to the terminal end ofthe boom assembly 24 is pressed downwardly against a surface or materialwith increasingly greater force.

In further implementations, the MRF joystick system 22 may vary the MRFresistance force impeding joystick movement in at least one direction asa function of another type of load placed on the work vehicle, such as acurrent load placed on the primary (e.g., internal combustion) engine ofa work vehicle engine. Additionally, while the previous descriptionprincipally focuses on altering the MRF resistance force based uponvariations on monitored work vehicle loads considered in isolation or anindependent sense, further embodiments of the MRF joystick system 22 mayadjust the MRF resistance force based upon changes in load (or anothermonitored work vehicle parameter mentioned herein) relative to anotherparameter or threshold value. For example, in certain embodiments, thecontroller architecture 50 may compare a monitored load to apredetermined threshold value (e.g., a particular minimum load valuestored in the memory 48) and implement the above-described MRFresistance force modifications only after a currently monitored loadsurpasses the threshold value. A similar approach may be utilized toassist operators in piloting a work vehicle to bring a load, such as thefill weight of a bucket, to a desired value, as in the case of a tipoffassist or control function described in the following paragraph.

Embodiments of the MRF joystick system 22 may monitor a current fillweight of an end effector or load-carrying implement and vary the MRFresistance force based of a differential between a target tipoff weightand the current fill weight of the implement, task. In this regard,certain work vehicle, such as wheel loaders, excavators, and similarwork vehicle equipped with fillable buckets, may be provided with atipoff control function, which assists an operator in utilizing the workvehicle to fill a receptacle (e.g., a bed of a dump truck) with adesired quantity of material. In this case, the MRF joystick system mayestimate the amount of material (e.g., by weight) utilizing any of themethods described herein (e.g., using a strain gauge, a load sensor, orany number of pressure sensors) and then utilize this information indetermining the manner in which to apply variances in the MRF joystickstiffness, thereby communicating to the operator that an appropriateamount of material is within the bucket to satisfy the establishedweight target of the dump truck (or other receptacle). With respect tothe example excavator 20, in particular, the controller architecture 50may first establish a target tipoff weight to which the bucket 26 isdesirably filled; e.g., by recalling from memory 48 a default setting ora setting entered into the excavator computer via operator interface 78.The controller architecture 50 may then selectively vary the MRFresistance force based of a differential between the target tipoffweight and the current fill weight of the bucket 26, as previouslydescribed. Such an MRF joystick response may be generated when firstfilling the bucket 26 (e.g., by increasing joystick stiffness, byproviding a detent effect, or by providing pulsating effect) when atarget bucket load is achieved. In other instances, the MRF joysticksystem may provide similar tactile cues assisting an operator withdumping-out an appropriate amount of material to satisfy the targetbucket load if the bucket 26 is inadvertently over-filled by theoperator when piloting the work vehicle.

With continued reference to STEP 204 of the example MRF machine statefeedback process 190 (FIG. 5), the controller architecture 50 mayfurther vary the MRF resistance force and, therefore, joystick stiffnessbased upon work vehicle ground speed in certain instances (parameter210). In one possible approach, the controller architecture 50 mayselectively increase the MRF resistance force impeding joystick motionin directions utilized to control vehicle steering at higher vehiclespeeds, with such an increase potentially performed gradually(continually) or in a stepwise fashion with any number of discreteresistance increase intervals. Such ground-speed depend increases injoystick stiffness may be applicable to the example excavator 20 whenoperable in a travel mode in which the heading and, perhaps, the groundspeed of the excavator 20 can be controlled utilizing theabove-described joystick devices 52, 54 (FIG. 2). Further, the MRFresistance force may be increased about the rotational axiscorresponding to steering of the excavator 20 in embodiments; and,perhaps, also the rotational axis corresponding to acceleration anddeceleration of the excavator 20 (in which case such progressiveincreases in the MRF resistance force may be provided only in thedirection of joystick rotation causing the excavator to accelerate).Such an approach is also usefully applied (and, perhaps, may be evenmore beneficial) in the case of work vehicles capable of traveling athigher ground speeds and/or in the case of work vehicles exclusivelypropelled in response to joystick controls, such as the example SSL 218described below in connection with FIG. 6. Generally, increasing MRFjoystick resistance at higher vehicle speeds may advantageously improvethe precision with which an operator may steer the work vehicle andprovide a better indicator of operator intent as an operator needovercome a greater force to move the joystick in an intended manner(thus reducing the likelihood of inadvertent joystick motions due tooscillations or other effects in the presence of high vibratory forcesoften occurring during work vehicle travel).

In still further implementations of the work vehicle MRF joystick system22, and as indicated in FIG. 5 by parameter 212, the controllerarchitecture 50 may selectively vary the MRF resistance force and,therefore, the joystick stiffness for trajectory shaping purposes.Specifically, in such embodiments, the controller architecture 50 mayvary the MRF resistance force as a function of the curve or profilefollowed by the work vehicle when transitioning from a current motionstate (e.g., work vehicle ground speed or steering angle) to anoperator-commanded motion state (e.g., a new work vehicle speed orsteering angle) when immediate transition to the operator commandedstate cannot be achieved or would be undesirable; e.g., would cause thework vehicle to lurch forward or to abruptly stop in the case ofacceleration or deceleration, or would cause the work vehicle todrastically change heading (and potentially become unstable) at higherground speeds. Accordingly, if the operator attempts to move thejoystick in a manner that would cause such an undesirably abrupt changein a machine state (e.g., abrupt acceleration, deceleration, or turningof the work vehicle), perhaps rapidly moving the joystick from a neutralposition to the end of its travel in a given direction, the MRF joysticksystem 22 may progressively increase the joystick stiffness as thejoystick rapidly moves from the neutral toward its end of travel (asindicated by the joystick rate of change). This may provide a betterindicator if the operator truly intends to command such an undesirablyabrupt change in the machine's motion state (improving the relationshipbetween operator expectation and machine behavior) and will better alignactual machine performance with joystick motion. This may also bedescribed as configuring the controller architecture 50 to (i) determinewhen motion of the joystick in an operator input direction at a detectedrate will result in an undesirably abrupt change in the current motionstate of the work vehicle; and (ii) when so determining, commanding theMRF joystick resistance mechanism to increase the MRF resistance forceto impede continued movement of the joystick in the operator inputdirection. A similar approach can also be utilized to promote smoothmovement or “trajectory shaping” of a joystick-controlled boom assembly,such as the boom assembly 24 of the example excavator 20 shown in FIGS.1 and 2.

In still embodiments of the work vehicle MRF joystick system 22, and asindicated by the example parameter 214 at STEP 204 of the MRF machinestate feedback process 190 (FIG. 4), the controller architecture 50 maymonitor the movement of one or more movable components of a work vehiclerelative to its range of travel; and, then, provide tactile feedback orcues via MRF resistance force variations as the moveable componentapproaches the end of its range of travel (herein, a “motion stop point”or a “motion stop”). Such a moveable component can be, for example, anarticulable joint of a work vehicle (e.g., a pin pivot joint of a boomassembly) or a hydraulic cylinder having a stroke limit or anarticulable joint of a boom assembly. To provide a more specificexample, and referring once again to the excavator 20 (FIGS. 1 and 2) asthe movement of a boom assembly 24 nears the end of its range of motionin a particular DOF, or as one or more of the hydraulic cylinders 38,40, 42 nears their respective stroke range limits, the controllerarchitecture 50 may vary the MRF resistance force inhibiting joystickrotation about an axis corresponding to movement of the component in amanner conveying to an operator (through tactile feedback) that thecomponent is approaching a motion stop. Such feedback may be provided byprogressively increasing the MRF resistance force resisting joystickmotion commanding movement of the moveable component (e.g., extension orretraction of a hydraulic cylinder) toward its end of travel.Alternatively, a pulsating effect or a brief detent effect may begenerated ahead of the moveable component reaching its end of travel;e.g., when a set percentage (e.g., 5%) of the stroke range of ahydraulic cylinder or cylinder pair remains as the cylinder(s) extend orretract in accordance with joystick commands. By providing suchMRF-applied tactile feedback through variations in joystick stiffness,operator awareness when a particular joystick-controlled componentapproaches its end of travel may be enhanced. Concurrently, a soft stopeffect is created to help cushion or reduce shock forces that mayotherwise be generated when the work vehicle part or assembly reachesits end of travel. A similar approach may also be utilized whenapproaching other limits of the work vehicle, such as when the EHactuation system 44 approaches a stall condition in response to operatorcommands entered via one or more MRF joystick devices.

In still further embodiments, the MRF joystick system 22 may selectivelyvary the MRF resistance force inhibiting joystick motion in at least oneDOF in a manner mimicking legacy systems familiar to operators, asindicated by parameter 215 listed in STEP 204 of the MRF machine statefeedback process 190 (FIG. 4). In this regards, certain operators may beaccustomed to interaction with mechanical joysticks having directmechanical connections to the hydraulic valves (e.g., pilot valves orspools) within an EH actuation system 22 may be disconcerted by the lackof such a direct “feel” connection when utilizing an EH joystick, whichconverts joystick motions to electrical signals transmitted to valvesolenoids or other actuators to perform such functions. Embodiments ofthe MRF joystick system 22 can advantageously retain the versatility andother benefits of EH control schemes, while selectively generatingjoystick behaviors mimicking purely mechanical system 22 s. Aspreviously alluded to, this may be accomplished by increasing the MRFresistance force, and thus increase joystick stiffness, as a function ofhydraulic pressures within the EH actuation system 22. Similarly, thecontroller architecture 50 may control the MRF joystick resistancemechanism to simulate lift-off or cracking of a (e.g., pilot) valve withthe EH actuation system 22 by, for example, initially generating ahigher MRF resistance force as a joystick is first displaced in a givendirection (the operator input direction) and then rapidly decreasing theMRF resistance force after movement of the joystick over a short rangeof travel in the operator input direction. Various other effects canlikewise be generated utilizing the MRF joystick system 22 to mimicother mechanical control characteristics or otherwise provide operatorswith a more uniform experience when transitioning from a mechanicaljoystick to an EH joystick control scheme.

In the above-described manner, embodiments of the MRF joystick system 22may provide operators with tactile feedback indicative of currentmachine states or parameters through selective increases in the MRFresistance force impeding joystick movement in at least one DOF. Suchfeedback is provided to an operator interacting with the above-describedMRF joystick devices in a highly intuitive and rapid manner. Furtherbenefits are achieved through the usage of MRF technology itself asopposed to the usage of other resistance mechanisms, such as actuatedfriction or brake mechanisms, also capable of selectively impedingjoystick motion when returning to a centered position after displacementtherefrom. Such benefits may include highly abbreviated response times;minimal frictional losses in the absence of MRF-applied resistanceforces; reliable, essentially noiseless operation; and other benefits asfurther discussed below. Additionally, embodiments of thebelow-described MRF joystick resistance mechanism may be capable ofgenerate a continuous range of resistance forces over a resistance forcerange in relatively precise manner and in accordance with commands orcontrol signals issued by the controller architecture 50. While theforegoing description principally focuses on a particular type of workvehicle (an excavator) including a particular joystick-controlled workvehicle function (boom assembly movement), embodiments of the MRFjoystick system 22 described herein are amenable to integration into awide range of work vehicles, as further discussed below in connectionwith FIG. 6.

Additional Examples of Work Vehicles Beneficially Equipped with MRFJoystick Systems

Turning now to FIG. 6, additional examples of work vehicles into whichembodiments of the MRF joystick system may be beneficially incorporatedare illustrated. Specifically, and referring initially to the upperportion of this drawing figure, three such work vehicles are shown: awheeled loader 216, a skid steer loader (SSL) 218, and a motor grader220. Addressing first the wheeled loader 216, the wheeled loader 216 maybe equipped with an example MRF joystick device 222 located within thecabin 224 of the wheeled loader 216. When provided, the MRF joystickdevice 222 may be utilized to control the movement of a FEL 226terminating in a bucket 228; the FEL 226, and front end loadersgenerally, considered a type of “boom assembly” in the context of thisdocument. Comparatively, two MRF joystick devices 230 may be located inthe cabin 232 of the example SSL 218 and utilized to control not onlythe movement of the FEL 234 and its bucket 236, but further controlmovement of the chassis 238 of the SSL 218 in the well-known manner.Finally, the motor grader 220 likewise includes two MRF joystick devices240 located within the cabin 242 of the motor grader 220. The MRFjoystick devices 240 can be utilized to control the movement of themotor grader chassis 244 (through controlling a first transmissiondriving the motor grader rear wheels and perhaps a second (e.g.,hydrostatic) transmission driving the forward wheels), as well asmovement of the blade 246 of the motor grader; e.g., through rotation ofand angular adjustments to the blade-circle assembly 248, as well asadjustments to the side shift angle of the blade 246.

In each of the above-mentioned examples, the MRF joystick devices can becontrolled to provide machine state feedback through intelligentMRF-applied variations in joystick stiffness. In this regard, any or allof the example wheeled loader 216, the SSL 218, and the motor grader 220can be equipped with a work vehicle MRF joystick system including atleast one joystick device, an MRF joystick resistance mechanism, and acontroller architecture. Finally, still further examples of workvehicles usefully equipped with embodiments of the MRF joystick systemsdescribed herein are illustrated in a bottom portion of FIG. 6 andinclude an FEL-equipped tractor 250, a feller buncher 252, a skidder254, a combine 256, and a dozer 258. In each case, the MRF joystickdevices can selectively vary the MRF resistance force impeding joystickmotion in at least one DOF to provide tactile feedback indicative of amonitored parameter pertaining to work vehicle at issue. Again, suchparameters can include work vehicle loads, ground speeds, and proximityof movable work vehicle component to motion stops. Variations in the MRFresistance force can also be utilized to simulate legacy systems (e.g.,to provide tactile feedback indicative of pilot valve lift-off) and/orto discourage (or to ensure operator intent in inducing) joystickmotions bringing about relatively abrupt changes in motion states of thework vehicles, as previously discussed.

Enumerated Examples of the Work Vehicle MRF Joystick System

The following examples of the work vehicle MRF joystick system arefurther provided and numbered for ease of reference.

1. In embodiments, a work vehicle MRF joystick system includes ajoystick device, an MRF joystick resistance mechanism, a controllerarchitecture, and a work vehicle sensor configured to provide sensordata indicative of an operational parameter pertaining to work vehicle.The joystick device includes, in turn, a base housing, a joystickmovably mounted to the base housing, and a joystick position sensorconfigured to monitor movement of the joystick relative to the basehousing. The MRF joystick resistance mechanism is controllable to varyan MRF resistance force resisting movement of the joystick relative tothe base housing in at least one degree of freedom. Coupled to thejoystick position sensor, to the work vehicle sensor, and to the MRFjoystick resistance mechanism, the controller architecture is configuredto: (i) monitor for variations in the operational parameter utilizingthe sensor data; and (ii) provide tactile feedback through the joystickdevice indicative of the operational parameter by selectively commandingthe MRF joystick resistance mechanism to adjust the MRF resistance forceimpeding joystick movement based, at least in part, on variations in theoperational parameter.

2. The work vehicle MRF joystick system of example 1, wherein theoperational parameter is a hydraulic load placed on the work vehicle,while the controller architecture is configured to command the MRFjoystick resistance mechanism to selectively increase the MRF resistanceforce with as the hydraulic load increases.

3. The work vehicle MRF joystick system of example 1, wherein the workvehicle includes an EH actuation system and an implement movableutilizing the EH actuation system, the operational parameter is acircuit pressure of the EH actuation system, and the work vehicle sensorincludes a pressure sensor configured to monitor the circuit pressure.

4. The work vehicle MRF joystick system of example 1, wherein the workvehicle includes a load-carrying component, the operational parameter isa material weight borne by load-carrying component, and the controllerarchitecture is configured to command the MRF joystick resistancemechanism to selectively increase the MRF resistance force with as thematerial weight increases.

5. The work vehicle MRF joystick system of example 4, wherein theload-carrying component of the work vehicle includes a boom-mountedimplement, while the controller architecture is configured to increasethe MRF resistance force in a manner impeding joystick movements raisingthe boom-mounted implement.

6. The work vehicle MRF joystick system of example 4, wherein theload-carrying component includes a receptacle of the work vehicle, whilethe operational parameter is a payload weight held by the receptacle.

7. The work vehicle MRF joystick system of example 1, wherein the workvehicle includes a bucket, and the work vehicle sensor is configured tomonitor a current fill weight of the bucket. The controller architectureis configured to: (i) establish a target tipoff weight to which thebucket is desirably filled, and (ii) selectively vary the MRF resistanceforce based of a differential between the target tipoff weight and thecurrent fill weight of the bucket.

8. The work vehicle MRF joystick system of example 1, wherein theoperational parameter is a ground speed of the work vehicle, while thecontroller architecture is configured to command the MRF joystickresistance mechanism to selectively increase the MRF resistance forcewith as the ground speed of the work vehicle increases.

9. The work vehicle MRF joystick system of example 8, wherein the MRFresistance force impedes joystick movement controlling at least one ofwork vehicle heading and work vehicle ground speed.

10. The work vehicle MRF joystick system of example 1, wherein the workvehicle includes a movable component having motion stop point, theoperational parameter is displacement of the movable component relativeto the motion stop point, and the controller architecture is configuredto command the MRF joystick resistance mechanism to selectively increasethe MRF resistance force as the movable component approaches the motionstop point.

11. The work vehicle MRF joystick system of example 10, wherein themovable component includes a hydraulic cylinder having a stroke limit oran articulable joint of a boom assembly.

12. The work vehicle MRF joystick system of example 1, wherein the workvehicle includes an EH actuation system containing a pilot valve, whilethe controller architecture is configured to command the MRF joystickresistance mechanism to selectively vary the MRF resistance force in amanner providing tactile feedback indicating when the pilot valveinitially opens.

13. The work vehicle MRF joystick system of example 1, wherein thejoystick device is utilized to control movement of the work vehicle, andthe operational parameter is a current motion state of the work vehicle.The controller architecture is configured to: (i) determine when motionof the joystick in an operator input direction at a detected rate willresult in an undesirably abrupt change in the current motion state ofthe work vehicle; and (ii) when determining when motion of the joystickin an operator input direction at a detected rate will result in anundesirably abrupt change in the current motion state of the workvehicle, command the MRF joystick resistance mechanism to increase theMRF resistance force to impede continued movement of the joystick in theoperator input direction.

14. The work vehicle MRF joystick system of example 13, wherein thejoystick device is utilized to control at least one of a ground speed ofthe work vehicle and a heading of the work vehicle.

15. The work vehicle MRF joystick system of example 13, wherein the workvehicle includes boom assembly attached to a chassis of the workvehicle, while the joystick device is utilized to control movement ofthe boom assembly.

CONCLUSION

The foregoing has thus provided work vehicle MRF joystick systemsconfigured to provide machine state feedback through variations in MRFresistance force. Such parameters can include, for example, variousloads applied to the work vehicle, ground speed of the work vehicle, andproximity of movable work vehicle component to motion stops. Further, insome embodiments, the MRF joystick system may vary an MRF resistanceforce impeding joystick motion in a manner simulating legacy systems inwhich a mechanical linkage is provided between a joystick and anactuated component, such as a pilot valve. In still otherimplementations in which the joystick device is utilized to controlmovement of the work vehicle, such as ground speed, heading, or boomassembly movements, the MRF joystick system may increase the MRFresistance force to discourage (or to confirm operator intent) joystickmotions resulting in relatively abrupt changes in the current motionstate of the work vehicle. In so doing, embodiments of the MRF joysticksystems intuitively provide tactile feedback enhancing operatorawareness of key parameters or conditions of the work vehicle to improveoperator satisfaction levels, improve efficacy in utilizing the workvehicle to perform various works tasks, and to provide other benefits,such as minimizing component wear in instances in which abrupt changesin work vehicle motion are reduced.

As used herein, the singular forms “a”, “an,” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The description of the present disclosure has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the disclosure in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of thedisclosure. Explicitly referenced embodiments herein were chosen anddescribed in order to best explain the principles of the disclosure andtheir practical application, and to enable others of ordinary skill inthe art to understand the disclosure and recognize many alternatives,modifications, and variations on the described example(s). Accordingly,various embodiments and implementations other than those explicitlydescribed are within the scope of the following claims.

What is claimed is:
 1. A work vehicle magnetorheological fluid (MRF)joystick system utilized onboard a work vehicle, the work vehicle MRFjoystick system comprising: a joystick device, comprising: a basehousing; a joystick movably mounted to the base housing; and a joystickposition sensor configured to monitor movement of the joystick relativeto the base housing; an MRF joystick resistance mechanism controllableto vary an MRF resistance force impeding joystick movement relative tothe base housing in at least one degree of freedom; a work vehiclesensor configured to provide sensor data indicative of an operationalparameter pertaining to work vehicle; and a controller architecturecoupled to the joystick position sensor, to the MRF joystick resistancemechanism, and to the work vehicle sensor, the controller architectureconfigured to: monitor for variations in the operational parameterutilizing the sensor data; and provide tactile feedback through thejoystick device indicative of the operational parameter by selectivelycommanding the MRF joystick resistance mechanism to adjust the MRFresistance force based, at least in part, on variations in theoperational parameter.
 2. The work vehicle MRF joystick system of claim1, wherein the operational parameter comprises a hydraulic load placedon the work vehicle; and wherein the controller architecture isconfigured to command the MRF joystick resistance mechanism to increasethe MRF resistance force as the hydraulic load increases.
 3. The workvehicle MRF joystick system of claim 1, wherein the work vehiclecomprises an electrohydraulic (EH) actuation system and an implementmovable utilizing the EH actuation system; wherein the operationalparameter comprises a circuit pressure of the EH actuation system; andwherein the work vehicle sensor comprises a pressure sensor configuredto monitor the circuit pressure.
 4. The work vehicle MRF joystick systemof claim 1, wherein the work vehicle comprises a load-carryingcomponent; wherein the operational parameter comprises a material weightborne by load-carrying component; and wherein the controllerarchitecture is configured to command the MRF joystick resistancemechanism to increase the MRF resistance force as the material weightincreases.
 5. The work vehicle MRF joystick system of claim 4, whereinthe load-carrying component of the work vehicle comprises a boom-mountedimplement; and wherein the controller architecture is configured toincrease the MRF resistance force in a manner impeding joystickmovements raising the boom-mounted implement.
 6. The work vehicle MRFjoystick system of claim 4, wherein the load-carrying componentcomprises a receptacle of the work vehicle; and wherein the operationalparameter comprises a payload weight held by the receptacle.
 7. The workvehicle MRF joystick system of claim 1, wherein the work vehiclecomprises a bucket; wherein the work vehicle sensor is configured tomonitor a current fill weight of the bucket; and wherein the controllerarchitecture is configured to: establish a target tipoff weight to whichthe bucket is desirably filled; and selectively vary the MRF resistanceforce based of a differential between the target tipoff weight and thecurrent fill weight of the bucket.
 8. The work vehicle MRF joysticksystem of claim 1, wherein the operational parameter comprises a groundspeed of the work vehicle; and wherein the controller architecture isconfigured to command the MRF joystick resistance mechanism to increasethe MRF resistance force as the ground speed of the work vehicleincreases.
 9. The work vehicle MRF joystick system of claim 8, whereinthe MRF resistance force impedes joystick movement controlling at leastone of work vehicle heading and work vehicle ground speed.
 10. The workvehicle MRF joystick system of claim 1, wherein the work vehiclecomprises a movable component having motion stop point; wherein theoperational parameter comprises displacement of the movable componentrelative to the motion stop point; and wherein the controllerarchitecture is configured to command the MRF joystick resistancemechanism to selectively increase the MRF resistance force as themovable component approaches the motion stop point.
 11. The work vehicleMRF joystick system of claim 10, wherein the movable component comprisesa hydraulic cylinder having a stroke limit or an articulable joint of aboom assembly.
 12. The work vehicle MRF joystick system of claim 1,wherein the work vehicle comprises an electrohydraulic (EH) actuationsystem containing a pilot valve; and wherein the controller architectureis configured to command the MRF joystick resistance mechanism toselectively vary the MRF resistance force in a manner providing tactilefeedback indicating when the pilot valve initially opens.
 13. The workvehicle MRF joystick system of claim 1, wherein the joystick device isutilized to control movement of the work vehicle; wherein theoperational parameter comprises a current motion state of the workvehicle; and wherein the controller architecture is configured to:determine when motion of the joystick in an operator input direction ata detected rate will result in an undesirably abrupt change in thecurrent motion state of the work vehicle; and when determining whenmotion of the joystick in an operator input direction at a detected ratewill result in an undesirably abrupt change in the current motion stateof the work vehicle, command the MRF joystick resistance mechanism toincrease the MRF resistance force to impede continued movement of thejoystick in the operator input direction.
 14. The work vehicle MRFjoystick system of claim 13, wherein the joystick device is utilized tocontrol at least one of a ground speed of the work vehicle and a headingof the work vehicle.
 15. The work vehicle MRF joystick system of claim13, wherein the work vehicle comprises boom assembly attached to achassis of the work vehicle; and wherein the joystick device is utilizedto control movement of the boom assembly.
 16. A work vehiclemagnetorheological fluid (MRF) joystick system utilized onboard a workvehicle, the work vehicle MRF joystick system comprising: a joystickdevice, comprising: a base housing; a joystick movably mounted to thebase housing; and a joystick position sensor configured to monitormovement of the joystick relative to the base housing; an MRF joystickresistance mechanism controllable to vary an MRF resistance forceimpeding joystick movement relative to the base housing in at least onedegree of freedom; and a controller architecture coupled to the joystickposition sensor and to the MRF joystick resistance mechanism, thecontroller architecture configured to: monitor a current ground speed ofthe work vehicle; and selectively command the MRF joystick resistancemechanism to adjust the MRF resistance force based, at least in part, onthe current ground speed of the work vehicle.
 17. The work vehicle MRFjoystick system of claim 16, wherein the controller architecture isconfigured to command the MRF joystick resistance mechanism toprogressively increase the MRF resistance force impeding joystickrotation about a first axis as the current ground speed of the workvehicle increases.
 18. The work vehicle MRF joystick system of claim 17,wherein the joystick device is controllable is steer the work vehicle byrotation of the joystick about the first axis.
 19. A work vehiclemagnetorheological fluid (MRF) joystick system utilized onboard a workvehicle having a boom-mounted implement, the work vehicle MRF joysticksystem comprising: a joystick device, comprising: a base housing; ajoystick movably mounted to the base housing; and a joystick positionsensor configured to monitor movement of the joystick relative to thebase housing; an MRF joystick resistance mechanism controllable to varyan MRF resistance force impeding joystick movement relative to the basehousing in at least one degree of freedom; and a controller architecturecoupled to the joystick position sensor and to the MRF joystickresistance mechanism, the controller architecture configured to:estimate a variable load resisting movement of the boom-mountedimplement in at least one direction; and selectively command the MRFjoystick resistance mechanism to increase the MRF resistance force asthe variable load increases.
 20. The work vehicle MRF joystick system ofclaim 19, wherein the variable load comprises a material weight carriedby the boom-mounted implement; and wherein the controller architectureis configured to command the MRF joystick resistance mechanism toincrease the MRF resistance force in a manner impeding joystick motionsraising the boom-mounted implement.